1. Technical Field
The disclosure relates generally to dynamoelectric machine suspension systems, and more particularly, to a spring bar stator core suspension system for a dynamoelectric machine.
2. Background Art
A stator core suspension for a dynamoelectric machine such as a generator or motor has to support the stator core and provide vibration isolation to the supporting structure (e.g., frame), which is mounted to the foundation. For example, large 2-pole generators may require vibration isolation to avoid shaking the foundation to such an extent that the anchorage will be compromised and environmental and health and safety (EHS) floor vibration limits may be exceeded.
FIGS. 1-4 illustrate a conventional stator core suspension 10 including two spring bars 12 (see FIG. 2). FIG. 1 shows a cross-sectional side view, and FIG. 2 shows a cross-sectional view along line A-A in FIG. 1. As understood, a plurality of keybars 14 are provided that each couple to a respective stator core section 13 of a group of circumferentially spaced stator core sections 13 that make up the stator core. Keybars 14 are also mounted to a frame 16 via spring bars 12, which provide vibration isolation. As shown best in FIG. 2, spring bars 12 are bolted on each side of keybar 14 such that they are mounted circumferentially relative to a stator core section 13 (shown in phantom). As shown in FIG. 1, the suspension is coupled to a frame 16 after frame mounts (e.g., bore ring) 18 inside diameters have been machined to size. Keybar 14 dovetails 20 are then used (measured relative to one another) to locate the keybar-to-spring bar assembly and a bolt and dowel mounting holes are line drilled in frame mount 18. FIG. 2 depicts the current bolted suspension system keybar-to-spring bar attachment in which shims 19 between spring bars 12 and keybar 14 are sized to limit spring bar bending stress. FIGS. 3-4 show two common spring bar to frame mount arrangements used to date. As shown in FIG. 3, two shoulder bolts 22 mount spring bar 12 to frame mount 18, or as shown in FIG. 4, two dowels 24 with a single cap screw 26 for clamping between the dowels mounts spring bar 12 to frame mount 18.
As shown best in FIGS. 1, 3 and 4, the above-described suspensions require milling relief portions 30, i.e., changes in cross-sectional area, in spring bars 12 to allow for optimization of a bounce frequency and stiffness of spring bars 12. The milling process is expensive. In addition, conventional systems require milling frame mounts and drilling and tapping spring bar mounting holes into completed frame fabrications, which can only be done at a limited number of locations in the world. Consequently, the costs of the suspensions are high and the amount of machining required to mount them is extensive.
Welded spring bar suspension systems are relatively inexpensive but require special skill and expertise to allow for weld distortion and achieve keybar positions within specified tolerances. Some manufacturers have overcome this problem by machining the keybar dovetails after fabrication is completed, thereby eliminating weld distortion. However, few manufacturers have this machining capability.